Facies Distribution of a High-Latitude Marginal Basin, McMurdo Sound, Antarctica

Louis R. Bartek, John B. Anderson

McMurdo Sound is a small marginal basin located in the southwestern part of the Ross Sea. Even though it is not a back-arc basin, it is characterized by many features that make it an excellent analog for back-arc basin sedimentation. Although this type of basin is commonly associated with high heat flow, it still may have hydrocarbon potential in young rocks that have yet to have their hydrocarbons cracked past the "petroleum window," and therefore may warrant increased exploration activity.

A detailed study of cores and high-resolution seismic data collected in the Sound was conducted to improve our understanding of the facies architecture in such a setting. The study revealed that the Sound has three facies belts whose locations are controlled by the combination of the proximity to sediment sources, sediment supply, and sedimentary processes. Coarse-grained, moderate to poorly sorted lithic arenites, sourced from the volcanic islands south of the Sound and the diverse bedrock geology of the Transantarctic Mountains, have been deposited on the western shelf and are believed to have been transported there via ice rafting and/or eolian processes. The central part of the Sound has been the site of deposition of diatomaceous oozes and muds, interbedded with ashes and distal urbidites, because of the quiescent oceanographic setting, remoteness from sources of terrigenous material, and because the area is affected by an influx of nutrient-rich waters from the north. The diatomaceous material has been reported to be enriched in organic carbon and could eventually be an excellent source rock for hydrocarbons. The steep eastern flank of the basin is blanketed by gravity-flow deposits that range from coarse-grained, poorly sorted grain flows and debris flows to well sorted fine-grained turbidites. Bathymetric and high-resolution seismic surveys indicate that these deposits are from both line and point sources, and that some point sources are separated by basement highs. These deposits lie ondip with the basin facies and could eventually become hydrocarbon reservo rs.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.